Chainplates

[Bill1565]

While the mast is down, I have to replace a couple of chainplate bulkheads due to rot. Gonna move the chain plates out also. Lowers are not currently symmetrical nor in line with the pull. Uppers are close to in line, but moving them out 3-4 inches won't change that much. What do you guys think about cutting out the head liner around the bulkheads and glassing the bulkheads to the deck as well as the hull?

 

[DianaOfBurlington]

'Glassing chainplate bulkheads

It's a very good idea. But use epoxy, not polyester (fiberglass) resin. You can use fast (205) hardener, but so long as you have all your ducks in line first wait a few moments just to let it start setting up before laying on the fiberglass cloth so it will stick overhead. Then roller it smooth-- no air bubbles.

Of course proper application will have you chip out rotten material (plywood), mend mechanically (physical fit), treat liberally with epoxy and then sand before applying the 'glass.

One terrific trick I got from a guy at the CY shop is to lay a fat bead of 5200 along the edge of the plywood prior to bonding it to the hull. Of course one should never 'glass over a flexible compound; but that's not the purpose of the 5200 here. The 5200 will fill the void between the slightly-uneven fit of the plywood against the inside the the hull or deck. Then, applying 'glass' with epoxy, you have a lovely wide fillet to roller against, avoiding the likelihood of having air bubbles in precisely the worst possible spot to have them.

In fact the 5200 alone might well take care of the whole problem-- again, with proper preparation first. I've done that in several places with no problems. (After all it does hold the keel on!)

One of the reasons why your bulkheads rotted in the first place was probably because they were 'treated' with polyester resin. Somewhere, at some time, water got in, dampened the plywood, caused the fiberglass to part company with it, and then managed to trap the moisture inside the wood. This is very very common. Proper preparation with WEST-system epoxy will prevent this in future.

I had/have the opportunity to 'glass the main bulkhead to the underside of the deck on Diana too. The worst possible case is that it would only crack from minor flexing this way and that, like from people walking on the deck, and epoxy isn't very flexible for that. (This is one thing the 5200-only approach will avoid.) The real reason I haven't done it is because the bulkhead is very sound and the deck core has been (more than) adequately filled with epoxy and, besides, I just don't feel like doing it. But one can always do it in future if needs be.

By the way, I would rather move the CPs inboard than outboard, to faciliate tighter jib sheeting. You have a cutter and this is of benefit for the inner jib. On Diana (an early H25) mine are bolted to the toerail. Believe me I did consider moving them. Skip Moorhouse, the sailmaker, had hull no.1 and he had his moved to the side decks. But the security of the angle-iron bolted to the full-length toerail outweighs the sail-trim concerns. Besides I am getting a higher-cut genny anyway, so the clew will be above the lifelines at that point.

What do you mean that the lowers are 'not symmetrical'? If they are different distances from the uppers that means that mast rake is leaning the uppers aft. Take a look at the C44 and you'll see mast rake to good effect. All my dad's boats had imposed mast rake. If they're where they were as-designed, don't change the locations fore-to-aft at all. Just be sure you have enough room on the forestay to let the mast rake aft (the C44 is 1:12; yours will be more like 1:20). Many furler installations incur so much headstay sag that the only remedy is to take up on it so tightly that the mast rake is obliviated; then the owner complains it won't point well. Be sure the furler is correct; or add a toggle.

 

[Bill1565]

Wow. That's a plate full. by not symmetrical I meant athwartships. Note the fwd lowers in the first two pictures. I wouldn't presume to second guess the designer on fore and aft location. Also wouln't want to relocate the bulkheads. I read here on the owners forum about G10 fiberglass panel. Was going to remove all the plywood in the rotten bulkheads and replace with that.

 

[DianaOfBurlington]

Bill--

1. Avoid the G10. It's very expensive, heavy, unnecessary, and will eat every edged tool you use on it (I am not exaggerating. You WILL need new saw blades). Patch the bulkhead with plywood closely matching what you have. Cut the rot/bad area out and make the new piece fit mechanically as well as you can. Treat all affected areas & edges with WEST epoxy, and when it dries check your fit again. When it's ready to go, duct-tape it in place on one side and, using epoxy with a bit of filler (just enough to keep it from being runny) and a putty knife, trowel up the edges and the gap. Work it in completely. When it's dry take off the duct tape and do the other side too. Sand fair when dry. This should be perfectly adequate.

After that you can decide to 'glass the bulkhead to the cabintop; but the 5200 method I mentioned will serve quite well.

Also-- consider using Durawhite to paint the bulkhead-- very traditional, bright and cheery, easy, and pretty. It bonds very well to otherwise-untreated epoxy. I've used it all over my boat.

2. I had not observed that your CPs were THAT much out of symmetrical. That looks like about 4 inches' difference. That's absurd. (BTW my point was that the boat was well designed. I never said Hunter Alachua was known for quality control!) If you have the opportunity I would remedy that. Just do yourself a favor and measure both sides. from the side face of the mast outboard to the shroud attachment pins, first. You might find a very odd surprise there.

Even if the boat is a little asymmetrical (mine is too), you can mitigate this difference by cheating a little each way. Maybe just choose one side to move. Mark the athwartships line of the bulkhead on the deck and removed the SS plates. Duct-tape the holes from the bottom and fill from above using glass fibers and epoxy. Then chop out a new hole using spade bitts, a saber saw and a Dremel, and reinstall the CPs where they belong better. (This is exactly how I fixed First Light, a 1977 C44, a few years ago when we replaced corroded SS chainplates.) Remember, don't obsess about a little inaccuracy-- any improvement to what you had is an improvement.

BTW, there is a lot of discussion about this, but I think I would tend to attach the CPs to your newly-epoxied bulkhead with 5200. These two substances, 5200 and epoxy, go very well together (in fact when one is applied while the other is still uncured they expedite the curing time of each other). 5200 is very good in a shear load, which is what CPs bolted to a bulkhead are in. The epoxy saturating the plywood is a very good surface for 5200 to bond to. Just sand a little and wash with mineral spirits or acetone first.

Whatever you do, replace ALL the attaching fasteners with new, preferably of 316, not 18-8, SS.

Also, avoid silicone to seal the CPs in the deck... unless you would like the deck to leak and soon rot the core and the bulkhead. This is also another good application for 5200. It's strong, flexible and able to keep out water. Just consider-- if this job is done right, how old will you be when you have to chip out the 5200 and fix that bulkhead again when it rots next time? (With silicone I predict it'll be about in 3 to 5 years. With 5200 I predict about 25-30. Do the math.)

 

[Bill1565]

wow. Again a lot to chew on. Thank you. Gotta run, I'm running a small boat regatta later today.